By definition you’d expect it to always be under 200 2 hours after a meal or glucose load, and under 126 after a fast.
If it was hitting 200 or above randomly without symptoms, I’d still suspect diabetes, or at least impaired glucose tolerance, a pre-curser to diabetes.
A sample curve is here: http://themedicalbiochemistrypage.org/images/glucosetolerancetest.jpg
Lots others can be found by typing “postprandial”, “glucose”, and “curve” into a google image search.
I’m not sure the OP’s title question has been answered here.
If I am reading it correctly, the OP wants to know how high a non-diabetic’s blood sugar could get…not what the definition of diabetes is according to an oral glucose tolerance test load.
Let’s take an individual with normal renal physiology and a normal oral glucose tolerance test. How high could you push his sugar?
A glucose tolerance test uses 1.75 grams of glucose per kilo, up to 75 grams of glucose, ingested on an empty stomach within 5 minutes. But what happens if we give a guy, say, 1,000 grams of glucose on an empty stomach? Let’s give him another 1,000 grams as soon as we can get it down him. And let’s keep doing it…How high can we push his sugar? It won’t be a test for diabetes, that’s for sure. I think this is the gist of the OP’s question.
I wish I knew the answer for him. I can comment on a few things, and that’s all, unfortunately.
First of all, let’s assume he can keep that huge load of glucose down without barfing. It won’t empty into the upper intestine where most glucose gets absorbed all at once, but let’s say a lot gets through and he starts getting this huge load of glucose into the blood stream.
Would it overload his capacity to carry it intracellularly using his endogenous insulin? I think it would. Even if his pancreas could keep up, I think the cellular transport mechanisms would be saturated. Now what happens?
Well, if his kidneys are normal, the proximal tubules grab all the glucose up until his blood sugar gets to 180 or so; when that renal threshold is reached (this varies by individual) he starts spilling sugar into the urine. The glucose creates its own osmotic drag and starts pulling free water with it, and he starts drinking water. This, of course, is the polyuria/polydypsia part of glucose out of control.
On average, most people don’t do a good job of keeping up with their free water loss, and I’d bet you could get a person with absolutely normal physiology pushed up over 200 or 250 with nothing but a huge oral glucose load. But if you are standing there encouraging him to just drown himself drinking water (and perhaps some electrolytes with it to keep up with those losses), I would be surprised if you could get a normal physiology much over 250 mg/dl of glucose with any size oral glucose load.
Now on the other hand, if you don’t water load him aggressively, all bets are off, and once you overload the intracellular transport, you are left with renal excretion to get rid of glucose. When that happens, and the patient gets dehydrated, I think even a person with totally normal physiology could have their glucose driven very very high–certainly all the way to non-ketotic hyperglycemic hyperosmolar coma. You’d basically poison them with glucose.
In short, without access to free water, a patient with otherwise normal physiology ingesting nothing but huge amounts of glucose could get very high blood sugars indeed, in my opinion.
Haven’t tried it, though.
Yeah, but is that restriction reasonable?
And wouldn’t adequate amounts of free water tend to blunt that glucose spike?
We just need a few volunteer dopers to test this out on…
Just reading your description of how to poison yourself with glucose is making my stomach roll. {insert barfing smiley}
